igneous
Granite
Granite (composed primarily of Quartz SiO₂, Alkali Feldspar KAlSi₃O–NaAlSi₃O–CaAl₂Si₂O₈, and Plagioclase Feldspar)
Hardness: 6-7 (Mohs scale); Color: Mottled pink, white, and gray (visible in specimen); Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: Feldspar shows two directions at 90 degrees, Quartz has no cleavage; Specific gravity: 2.65-2.75.
- Hardness
- 6-7 (Mohs scale)
- Color
- Mottled pink, white, and gray (visible in specimen)
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Mottled pink, white, and gray (visible in specimen); Luster: Vitreous to pearly; Crystal structure: Phaneritic (coarse-grained); Cleavage: Feldspar shows two directions at 90 degrees, Quartz has no cleavage; Specific gravity: 2.65-2.75.
Formation & geological history
Formed by the slow crystallization of magma below the Earth's surface (intrusive). Geological age spans from the Archean Eon to the Cenozoic, found globally in continental crust.
Uses & applications
Used extensively in construction (countertops, floor tiles, paving stones), as an abrasive, and for ornamental monuments or gravestones due to its durability and polish.
Geological facts
Granite makes up a large portion of the continental crust. Half Dome in Yosemite National Park is a massive granite monolith. It is one of the hardest and most durable common stones on Earth.
Field identification & locations
Identify in the field by its 'salt and pepper' or mottled appearance with visible interlocking crystals. Look for the pink/orange tint of orthoclase feldspar and the glassy look of quartz. Found in mountainous or shield areas globally.
